Kaan Luum Lagoon

It's a freedive training site about 15 mins drive from Tulum. The depth of the lagoon can reach 75m and there water has lots of layers and different texture and visibility at different depth (halocline), which looks pretty interesting.

You can always just swim there, the water is very shallow at the edge (1 meter) so very good for families. But the visibility is not as clear.